Signed-off-by: Yong Zhao <yozhao@microsoft.com>

1.Fix the format of alerting message.
2.For each exited process, there are two fields: the time of last alert
and number of dead minutes. Use a dict to hold these two fields instead
of a list.
3.Use a formula to calculate how many minutes the process was in dead
state instead of hard code.

Signed-off-by: Yong Zhao <yozhao@microsoft.com>